Speed reducing gearing



22, 1941 B.IFOIOITE,IJR .1

SPEED REDUCING GEARING 3 Sheets-Shet 1 Filed uarh- 11, 1940 July 22, 1941., B, FOQTE, JR 2,250,259

- SPEED REDUCING GEARIXG I Filed March 11 1940 3 Sheets-Sheet 2 Patented July 22, 1941 UNITED STATES PATENT OFFICE 2,250,259 SPEED REDUCING Gamma Bradford Foote, In, River Forest, Ill. Application March 11, 1940, Serial No. 323,278

3 Claims.

The invention relates to hello-centric speedreducing gearing.

In speed-reducing gearing, a desideratum to produce a construction of maximum capacity.

with gears or in a unit as small as possible.

Hello-centric gearing lends itself to high ratio or great variation in speed-reduction but, so far as I am aware, has not been extensively adopted for industrial uses on account. of the low efficiency or high power losses in prior constructions.

The primary object of the present invention is to provide hello-centric speed-reducing gearing of high eflioiency and in which power losses are reduced to theminimum and which is capable of being embodied in a. small unit for various industrial uses.

In hello-centric gearing with teeth of standard profiles in internally and externally toothed meshing gears, the minimum difference of five between the number of teeth in the gears has been generally recognized as necessary to provide clearance for the meshing and unmeshing of the teeth. This difference necessitated the movement of the mass in the epicycloidal gear by the eccentric a distance at least as great as the difierence between the pitch circles of that gear and the stationary gear and resulted in a loss of power or decreased efilciency proportionate to the radial movement of the mass in the epicycloidal gear. Therefore, a desideratum, for achieving efiiciency in eccentric lever gearing, is to reduce the diametric travel of the epicycloidal gear and the throw of the eccentric to the lowest possible minimum. Another object of. the invention is to provide a construction of hello-centric gearing in which the radial travel of the epi--. cycloidal gear is held to the lowest minimum necessary for the meshing and unmeshing of the coacting gears during each revolution of the eccentric, so as to eliminate, so far as possible, the power losses resulting from such movement.

Where 'intern'ally and externally toothed gears having tooth-profiles adapted for line engagement between the meshing teeth, are used in hello-centric gearing, relatively large gears are necessary for high loads or capacities. Another. object of the invention is to provide a construction in which the engaging tooth-faces oi the gears are substantially straight and parallel during their engagement so that the load will be distributed throughout great areas and so that, during operation, approximately one-sixth of all oi the teeth of the gears will be simultaneously engaged wholly or partially for the corresponding distribution of the load. Such aicons'truction makes it possible to provide a comparatively small unit of exceptionally high capacity.

Another object of the invention is to reduce the load imposed on the bearings between the eccentric and the epicycloidal gear and to provide the meshing gears with side-faces which reduce the sliding engagement of the tooth-faces to the practical minimum, by providing the teeth with side-faces, such pitch-angles, and imparting movement to the teeth in such a paththat the lines of action will be substantially tangential to the pitch-circles of secondary reduction-gearing and will cause the tooth-faces to be moved parallel-wise to and from each other in the movement of the epicycloidal gear.

Another object of the invention is to provide a gearing in which all of the foregoing advantages and eiliciencies are combined to provide a unit of this type which is efficient in operation, is durable, has a high capacity for its size, and overcomes the inefliciencies and power losses of prior constructions. I

Other objects of the invention will appear from the detail description.

The invention consists in the several novel features which are hereinafter set forth and are more particularly defined by claims at the conclusion hereof.

In'the drawings: Fig. 1 is a longitudinal section of speed-reducing gearing embodying one form of the invention. Fig. 2 is a vertical section taken on line 22 of Fig. 1. Fig. 3 is a view illustrating the tooth-profiles and the movements of the teeth of the epicycloidal gear relatively to the stationary gear and also illustrating in dotted lines the gears of the secondary reduction of Figs. 1 and 2. Fig. 4 is an enlarged diagrammatic view illustrating the path of one of the teeth of the epicycloidal gear in its movement from one tooth to the next of the stationary gear. Fig. 5 is a longitudinal section of a modified form of the invention. Fig. 6 is an enlarged detail of the profiles. of the teeth of a coacting pairof gears.

The unit illustrated in Figs. 1 and 2, as an exemplification of the invention, comprises a case which encloses the gearing and is provided with a suitable base, an annular wall I0, and an integral wall II at one of its ends and a remov able head l2 at its opposite end. The speed reducing gearing is insertable into and removable from the case through the open end which is closed by the head it. A, high speed or in-put shaft I I is journaled in a. ball-bearing M which is mounted in the head l2. A low speed or outi put shaft i5 is coaxial with shaft i4 and is journaled in ball-bearings l8 which are carried by an inwardly extending cylindrical member ll which is integral with the end wall II. An eccentric I8 for driving the gearing between shafts i3 and I 5 is integrally formed on shaft l3. The case I0 is adapted to contain 011 for-lubricating all of the parts within the case and is provided with a plug 33 for delivering oil into the case.

centric with the eccentric l2.

A ring i2 is ioumaled on ball-bearings 22 which extend around and are mounted on the eccentric is, so that the ring is rotatable around the axis of, and movable radially by, eccentric l8. A ring 2| is fixedly secured, by a. key 22, against rotation in gear-case l0. Ring 2| is provided with internal gear-teeth forming a gear 22 having a pitch-circle concentric with the axis a of shaft l2. Ring I2 is provided with external teeth which form a gear 24 which meshes with gear 22 and has a pitch-circle which is con- Gear 22 and eccentric l8, upon rotation of the latter by and with shaft i2, produce epicycloidal movement of gear 24 and ring i2. These internally and externally toothed-gears and eccentric function as a primary speed-reduction of the heliocentric type.

Ring I2 is held against endwise movement relatively to the eccentric I! by locking-rings 2| which interflt with the outer races of ball-bearings 20. A counterbalance 22 is keyed to shaft i2 between eccentric l2 and ball H. An oil-seal ring I2 is provided around in-put shaft l2 and carried by the head l2 and a similar oil-seal ring l" around out-put shaft i5 is carried by a cap Iii which is secured to the end-wall ll of case l0. An externally-toothed gear 26 concentric with gear 24, is cut on ring l2. Gear 26 meshes with an internally-toothed gear 21 on a wheel 22 which is rigid or integral with the out-put shaft IS. The inner end of the in-put shaft i2 is journaled in a ball-bearing 20 which is mounted in wheel 22. Gear 22 travels epicycloidally with gear 24 and drives the wheel 22 and shaft l5. Gears 22 and 21 function as a secondary speedreduction of the unit. Gear 21 is concentric with the in-put shaft I 2 and the out-put shaft ii. In the construction of the secondary reduction illustrated in Figs. 1 and 2, in which the externally-toothed gear is epicycloidal and drives an internally-toothed out-put gear, the ratio is a multiplication of the ratio of the gear 24 to the gear 22 and the ratio of the gear 22 to the out-put gear 21.

In Fig. 5 the invention is exemplified in speedreducing gearing in which the ring I! of the primary reduction is provided with an internallytoothed gear 28 which meshes with and has its pitch-circle concentric with gear 24 on said ring and with eccentric Id. In this modification the ratio between gears 22, 21 is a difl'erential of the ratio between the eccentric gear 24 to the stationary gear 22 and the internal gear 22 to the out-put gear 22. Except for the difference in construction in the secondary gearing, the unit is the same in construction as that illustrated in Figswl and 2 and the description of Figs. 1 and 2 is applicable to both forms of the invention.-

Figs. 3 and 4 illustrate the operation of the gears of the primary reduction embodied in the constructions of Figs. 1, 2 and 5, according to the relative dimensions and contours of a commercial unit, by which the objects and advantages of the invention are attained. This specific construction is of a unit in which the stationary internally-toothed gear 22 has eighty-one teeth of ten diametral pitch and a pitch-diameter of 8.140" indicated at a: the epicycloidal gear 24 journaled on eccentric II has eighty teeth of ten diametral pitch and a pitch-diameter indicated at b of 8.000": the side-faces a of the teeth on gear 24 and the side-faces b of the teeth of gear 22 are substantially straight and have a pitch-angle of 37; the teeth of both gears have an addendum of .070" and a dedendum of .090"; the ends a of the teeth of gear 24 and the ends b of the teeth of gear 22 are rounded, as at a, b, respectively, on a radius not less than onehalf of the theoretical addendum; and the throw of the eccentric is .140" which is equal to the difference in the pitch-diameters of the gears.

;A slight clearance is necessary and is provided between the teeth of gears 22, 24, for the fulcruming of gear 24 on the teeth of gear 22 during the rotation of the eccentric. The throw of the eccentric is sumcient, but not substantially more than is necessary, to permit the outer curved ends l: of gear 24 to move across the curved ends a of the teeth of gear 22 at the point of their maximum radial inward movement by the eccentric and diametrically opposite to the point of maximum interfltting of the teeth of said gears at the limit of the outward movemrnt oi gear 24 by the eccentric. Each revo ution of the eccentric imparts an epicycloidal 1'3 of gear 24 due to the engagement of with stationary gear, 22 and rotates gear distance equal to the pitch of the teeth of gear 24 or a sufllcient distance to engage the succeeding tooth of gear 24. The rounded ends of the gear-teeth of both gears 22, 24 are provided to reduce the radial travel necessary for clearance between the teeth in the epicycloidal movement of gear 24 and,- with very slight clearance between the engaging teeth, permit the fulcruming of the gear 24 on the teeth of the gear 22 for the lever movement imparted to the epicyline b". The profiles of the'teeth of gears 22, 24

are illustrated on an enlarged scale in Fig. 6.

From Figs. 3 and 4; it will be seen that the tooth-path of the epicycloidal gear, with the throw of the eccentric, the tooth-profile, and pitch-circles of the gears described, result in bringing the side-faces a of the teeth of gear 24 and the side-faces b of gear 22 parallel-wise into successive pressure engagement, maintain whole or partial simultaneous engagement of a large number of teeth on the gears at all times, utilize the minimum eccentric throw and radial movement of the epicycloi-d-al gear, and cause the teeth of gear 24 to move to and from the teeth of gear 22 with minimum sliding engagement.

In traversing the path indicated by the line b in Fig. 4, the side-faces b of the teeth of gear 24 and the side-faces a of gears 22 become parallel immediately before the faces b pass into pressure engagement with the faces a and remain parallel during the initial movement of the faces b out of such engagment. This results from the travel of the eccentric across the diametrical line intersecting the center of the engaging tooth of gear '24 and the axis of rotation of the eccentric.

tooth-faces and produce lines 01 action which do the secondary reduction.

not impose heavy loads on the bearings between the eccentric and ring IS. The lines of action are substantially perpendicular to the engaging toothed-faces and approach tangency to the pitch-circles of the gears of the secondary reduction.

Approximately one-sixth of the entire number of teeth in gears 23, 24 are either wholly or partially engaged at all times. In consequence of this, the load is correspondingly distributed throughout approximately one-sixth of the gearteeth, in lieu of being concentrated on a single In practice, it has been found that the highest efficiency is attained in gearing embodying the invention in which there is a difierence of but one tooth in th number of teeth in the fixed and epicycloidal gears, but in some instances an advantage in efiiciency can be attained in constructions in which the difference is not greater than three. It has also been found in practice that in this gearing a pitch-angle of 37 in the teeth in the gears is the optimum and is highly efiicient and that in some instances the efiiciency can be improved if the pitch-angl of the teeth is kept between 35 and 41.

The invention exemplifies hello-centric speedreducing gearing, which is of high efficiency in operation, and makes it possible to utilize gearing of this type in a comparatively small'unit for high ratio speed-reduction of high capacity and in a wide range of variation in speeds by variation in the secondary reduction. I

The invention is not to be understood as restricted to the details set forth, since these may be modified within the scope of theappended claims, without departing from the spirit and scope of the invention.

into engagement, the contiguous straight side faces of the teeth on the gears being parallel in their fully meshing position, the radial portions of said path effecting the meshing of the teeth 5 so substantially the entire area of the contiguous side faces will pass into substantially parallel pressure engagement.-

, 2. Speed-reducing gearing comprising a driven shaft, an eccentric on, and rotatable with, said shaft, a stationary internally toothed gear, a

planetary externally toothed drivinggear meshing with the stationary gear, journaled on, and driven by, the eccentric, the teeth of said ears having rounded ends, v-shaped profiles, straight side faces and rounded apices, the throw of the their initial withdrawal from the teeth of the staeccentric and the pitch angle of the teeth being co-related so that the path of the teeth on the externally toothed gear will be substantialy radially'inward from full meshing position during tionary gear, then in an arc of a predetermined diameter during their further withdrawal and then circumferentially on an arc of greater diameter approximating a straight path around the apices of the teeth of the stationary gear,

then successively on a reverse arc of said predetermined diameter and then substantially radially outward into engagement with the teeth of the stationary gear to bring the side faces of the teeth of the gears into engagement, the side faces of the contiguous teeth being parallel and engaged throughout substantially their entire straight areas in their fully meshing position, the radial portions of said path efiecting the meshing and unmeshing of the-teeth so their side faces shaft, a stationary internally toothed gear, a

planetary externally toothed driving gear meshing with the stationary gear, journaled on, and driven by the eccentric, the teeth of said gears having 'roundedends, V-shaped profiles, straight 5 side faces and rounded apices, the throw of the Having thus described the invention, what I regard as new and desire to secure by Letters Patent is:

1. Speed-reducing gearing comprising a driven shaft, an eccentric on, and rotatable with, said shaft; a stationary internally toothed gear, a planetary externally toothed driving gear meshing withthe stationary gear journaled on, and driven by the eccentric, the teeth of both of said gears having rounded ends, V-shaped profiles, straight side faces, and rounded apices, the throw oi the eccentric and the pitch angleof the teeth being co-related so that the path of the teeth on the externally toothed gear will be substantially eccentric and the pitch angle of the teeth being co-related so that the path of the teeth on the externally toothed gear will be substantially radially inward from full meshing position during their initial withdrawal from the teeth of the stationary gear, then in an arc of a predetermined diameter during their further withdrawal, then circumferentially on an arc of greater diameter approximating a straight path around the apices of the teeth of the stationary gear,

radially inward from full meshing position during their initial withdrawal from the teeth of the stationary gear, then in an arc of a predetermined diameter during their further withdrawal, then circumferentially on an arc of greater diameter approximating a straight path around the apices of the teeth of the stationary gear,

then suocessivelyon a reverse arc of said predetermined diameter, and then substantially radially outward into engagement with the teeth of the stationary gear to bring the teeth of the gears into engagement, the contiguous side faces of the teeth on the gears being parallel and engaged throughout substantially their entire straight area'in their fully meshing position, the radial portions of said path eifecting the meshing and 5 unmeshing of the teeth so their side faces will pass into substantially parallel pressure e mement, the throwot the eccentric being adapted to. produce the circumferential portion of said tooth-path with only slight clearance around the teeth of the stationary gear.

BRADFORD FOOTE. J R. 

